The present invention relates to semiconductor optoelectronic devices in general and, more particularly, to wavelength tunable surface emitting semiconductor lasers and wavelength tunable filters.
Tunable wavelength Fabry-Perot based filters and VCSELs find a variety of applications in WDM telecommunications equipment. The wavelength tunability of these devices originates from the Fabry-Perot cavity gap change under the influence of a control signal. The tuning curve function describing the relationship between the control signal and the wavelength of the filter passband or the lasing wavelength is usually highly dependent on environmental conditions and changes with time due to polarization effects in the structure. In a first case, which involves WDM systems where the transmission channel wavelength has to comply with ITU grid, it is very important to precisely lock the lasing wavelength of a tunable laser to a particular wavelength value on the grid. In a second case, which involves tunable add/drop applications, the tunable laser must also be locked to a particular ITU channel. In a third case, which involves scanning applications, it is important to know the passband wavelength at a given moment in time to identify the ITU channel that the system is sampling. The first two cases are referred to as wavelength locking. The third case is known as wavelength referencing.
In accordance with an aspect of the present invention, a method and apparatus are provided for using the electrical characteristics of an opto-electronic device to measure the optical behavior of that device. The benefit of the present invention is the elimination or significant reduction of optical wavelength reference hardware that is currently required for wavelength referencing and locking. Accordingly, the present invention reduces the cost and complexity of the optical packaging of tunable opto-electronic telecommunication components. Furthermore, the present invention also significantly simplifies optical and electronic design of system level products with tunable opto-electronic devices. It is important to note that optical and electrical wavelength locking and referencing techniques do not mutually exclude each other and can be combined in many different ways to compliment each other.
The above and other features of the invention, including various novel details of constructions and combinations of parts, and other advantages, will now be more particularly described with reference to the accompanying drawings and pointed out in the claims. It will be understood that the particular method and apparatus embodying the invention are shown by way of illustration and not as a limitation of the invention. The principles and features of this invention may be employed in various and numerous embodiments without departing from the scope of the invention.